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/ shallow alluvial groundwater monitor xell (HGDAL6) in 2005 upgradient of the <br />t Loadout at a location adjacent to Dry Creek belox the confluence of Stokes Gulch <br />and Dry Creek (sea Exhibit 12-2, Surface Water Control Plan). The groundwater in <br />this wall will be sampled for the same parameters and frequency as well HGDAL3. <br />The impact assessment methodology will employ Mann-Kendall non-parametric trend <br />tests (Kendall, 1975) and Sen slope plots (Gilbert, 1987). Non-parametric <br />statistical analyses will be used because water quality data typically is not <br />normally distributed and the non-parametric tests are more resistant to the effects <br />of outliers. The analyses will focus on detecting persistent degradational trends. <br />Impacts associated with irrigation flows and dryland farming flows or seeps should <br />be seasonal in nature (exhibits some parameter concentration oscillations) but <br />should not show persistent worsening. The coal stockpile and sanitary usage is <br />year round and one should expect to see persistent degradational changes if impacts <br />are truly being caused by the Loadout. <br />Impact significance is linked to water uses and use potential. One cannot degrade <br />a water source that is already degraded to the point there is no use utility. This <br />is the case of the alluvial aquifer opposite and immediately downgradient of the <br />~~~ Loadout. Stream water quality at and downstream of the Loadout does have a water <br />use potential (marginal at times) and the use potential is livestock drinking <br />water. The trend analysis technique will focus on analysing parameter data sets <br />where there is very limited or no censoring (less than detection limit} and <br />particularly those parameters for which there are livestock standards (i.e., <br />sulfate, TDS, chloride, and boron). If persistent degradational impacts are <br />determined, the impact significance shall be assessed based on the magnitude of <br />change adjacent to the Loadout and the potential downstream extent of the <br />measurable degradation (i.e., could this magnitude of concentration increase <br />significantly affect a downstream hydraulically connected water source). in the <br />case of the alluvial aquifer, there is no downstream use, but there is flood <br />irrigation being practiced approximately 1.5 miles below the Loadout. The <br />principal source of water fox the flood irrigated fields is the Yampa Aiver via <br />Walker Ditch; however, there is the potential for Dry Creek water to also enter <br />Walker Ditch. It is unknown at this time as to whether there is upward flow from <br />the alluvium into the Dry Creek streamflow in the lower reaches of Dry Creek, but <br />the possibility cannot be ruled out because they are in hydraulic communication <br />with each other. If the persistent degradational change is measured at HGDAL3 <br />~~ which exceeds historically documented ranges for sulfate, TDS, and chloride at <br />TR-06 7 Revised 06/05 <br /> <br />